This invention relates to energy saving devices for fluorescent light systems and, more particularly, to an add-on device for connection in series with one lamp of a two-lamp rapid-start-type fluorescent light system to reduce by a predetermined amount the nominal electrical consumption of the system.
The majority of fluorescent lighting systems are of the so-called two-lamp rapid-start type in which the lamp electrodes are preheated for a very short time by a relatively low heater voltage, with the full open-circuit voltage thereafter applied to one of the lamps, causing it to start. An impedance parallels the second lamp and the voltage drop thereacross then causes the second lamp to start. Thereafter, the two lamps operate in series. This lighting system gives excellent performance and excellent lamp life.
In recent years, there has been considerable emphasis on reducing electrical energy consumption in existing fluorescent lamp systems and one such system is disclosed in U.S. Pat. No. 3,954,316, dated May 4, 1976 to Luchetta. In this system, an isolation transformer is connected in circuit with one of the heater windings for a lamp electrode and a power-reducing capacitor is connected between the primary and secondary of the isolation transformer. When the lamps are operating, the additional capacitor in circuit reduces the power consumed by the system by a predetermined amount. The use of capacitors in series with a rapid start type system to vary the power consumption thereof is also shown in U.S. Pat. No. 3,911,320, dated Oct. 7, 1975 to Crawford.
In U.S. Pat. No. 4,082,981, dated Apr. 4, 1978 to E. W. Morton, the present applicant, and J. F. Gilmore is disclosed an add-on type energy saving device for a fluorescent lamp system wherein two positive temperature coefficient of resistance (PTC) resistors complete the circuit to one of the lamp electrodes and a power reducing capacitor is connected in shunt with one of the PTC members. When the system is energized, heater current is passed through the lamp electrodes, which causes the PTC members to heat and rapidly rise in resistance. This places the shunting capacitor in series with the operating lamps, thereby reducing the power of the system.
Electronic time delay circuits which introduce a predetermined time delay for actuation of a relay coil are known and a typical circuit is described in U.S. Pat. No. 3,098,953, dated Aug. 1, 1960 to Herr. Another type of such circuit arrangement which utilizes a unijunction transistor is shown in U.S. Pat. No. 3,320,440, dated May 16, 1967 to Reed.
A rectifier and voltage doubler circuit as used in conjunction with an energizing circuit for a discharge lamp is disclosed in U.S. Pat. No. 3,931,544, dated Jan. 6, 1976 to Pitel.
The basic two-lamp rapid-start fluorescent light system is disclosed in U.S. Pat. No. 2,796,554, dated June 18, 1957 to Strecker.